#!/bin/sh
#* reason                       -- why this script was called, one of: pre-init connect disconnect
#* VPNGATEWAY                   -- vpn gateway address (always present)
#* TUNDEV                       -- tunnel device (always present)
#* INTERNAL_IP4_ADDRESS         -- address (always present)
#* INTERNAL_IP4_NETMASK         -- netmask (often unset)
#* INTERNAL_IP4_NETMASKLEN      -- netmask length (often unset)
#* INTERNAL_IP4_NETADDR         -- address of network (only present if netmask is set)
#* INTERNAL_IP4_DNS             -- list of dns serverss
#* INTERNAL_IP4_NBNS            -- list of wins servers
#* CISCO_DEF_DOMAIN             -- default domain name
#* CISCO_BANNER                 -- banner from server
#* CISCO_SPLIT_INC              -- number of networks in split-network-list
#* CISCO_SPLIT_INC_%d_ADDR      -- network address
#* CISCO_SPLIT_INC_%d_MASK      -- subnet mask (for example: 255.255.255.0)
#* CISCO_SPLIT_INC_%d_MASKLEN   -- subnet masklen (for example: 24)
#* CISCO_SPLIT_INC_%d_PROTOCOL  -- protocol (often just 0)
#* CISCO_SPLIT_INC_%d_SPORT     -- source port (often just 0)
#* CISCO_SPLIT_INC_%d_DPORT     -- destination port (often just 0)

# FIXMEs:

# Section A: route handling

# 1) The 3 values CISCO_SPLIT_INC_%d_PROTOCOL/SPORT/DPORT are currently being ignored
#   In order to use them, we'll probably need os specific solutions
#   * Linux: iptables -t mangle -I PREROUTING <conditions> -j ROUTE --oif $TUNDEV
#       This would be an *alternative* to changing the routes (and thus 2) and 3)
#       shouldn't be relevant at all)
# 2) There are two different functions to set routes: generic routes and the
#   default route. Why isn't the defaultroute handled via the generic route case?
# 3) In the split tunnel case, all routes but the default route might get replaced
#   without getting restored later. We should explicitely check and save them just
#   like the defaultroute
# 4) Replies to a dhcp-server should never be sent into the tunnel

# Section B: Split DNS handling

# 1) Maybe dnsmasq can do something like that
# 2) Parse dns packets going out via tunnel and redirect them to original dns-server

#env | sort
#set -x

# =========== script (variable) setup ====================================

PATH=/sbin:/usr/sbin:$PATH

OS="`uname -s`"

DEFAULT_ROUTE_FILE=/var/run/vpnc/defaultroute
RESOLV_CONF_BACKUP=/var/run/vpnc/resolv.conf-backup
FULL_SCRIPTNAME=/usr/sbin/vpnc
SCRIPTNAME=`basename $FULL_SCRIPTNAME`

# some systems, eg. Darwin & FreeBSD, prune /var/run on boot
if [ ! -d "/var/run/vpnc" ]; then
	mkdir -p /var/run/vpnc
fi

# stupid SunOS: no blubber in /usr/local/bin ... (on stdout)
IPROUTE="`which ip | grep '^/' 2> /dev/null`"

if [ "$OS" = "Linux" ]; then
	ifconfig_syntax_ptp="pointopoint"
	route_syntax_gw="gw"
	route_syntax_del="del"
	route_syntax_netmask="netmask"
else
	ifconfig_syntax_ptp=""
	route_syntax_gw=""
	route_syntax_del="delete"
	route_syntax_netmask="-netmask"
fi

if [ -x /sbin/resolvconf ]; then # Optional tool on Debian, Ubuntu, Gentoo
	MODIFYRESOLVCONF=modify_resolvconf_manager
	RESTORERESOLVCONF=restore_resolvconf_manager
elif [ -x /sbin/modify_resolvconf ]; then # Mandatory tool on Suse earlier than 11.1
	MODIFYRESOLVCONF=modify_resolvconf_suse
	RESTORERESOLVCONF=restore_resolvconf_suse
else # Generic for any OS
	MODIFYRESOLVCONF=modify_resolvconf_generic
	RESTORERESOLVCONF=restore_resolvconf_generic
fi

# =========== tunnel interface handling ====================================

do_ifconfig() {
	if [ -n "$INTERNAL_IP4_MTU" ]; then
		MTU=$INTERNAL_IP4_MTU
	elif [ -n "$IPROUTE" ]; then
		DEV=$($IPROUTE route | grep ^default | sed 's/^.* dev \([[:alnum:]-]\+\).*$/\1/')
		MTU=$(($($IPROUTE link show "$DEV" | grep mtu | sed 's/^.* mtu \([[:digit:]]\+\).*$/\1/') - 88))
	else
		MTU=1412
	fi

	# Point to point interface require a netmask of 255.255.255.255 on some systems
	ifconfig "$TUNDEV" inet "$INTERNAL_IP4_ADDRESS" $ifconfig_syntax_ptp "$INTERNAL_IP4_ADDRESS" netmask 255.255.255.255 mtu ${MTU} up

	if [ -n "$INTERNAL_IP4_NETMASK" ]; then
		set_network_route $INTERNAL_IP4_NETADDR $INTERNAL_IP4_NETMASK $INTERNAL_IP4_NETMASKLEN
	fi
}

destroy_tun_device() {
	case "$OS" in
	NetBSD) # and probably others...
		ifconfig "$TUNDEV" destroy
		;;
	esac
}

# =========== route handling ====================================

if [ -n "$IPROUTE" ]; then
	fix_ip_get_output () {
		sed 's/cache//;s/metric \?[0-9]\+ [0-9]\+//g;s/hoplimit [0-9]\+//g'
	}

	set_vpngateway_route() {
		$IPROUTE route add `$IPROUTE route get "$VPNGATEWAY" | fix_ip_get_output`
		$IPROUTE route flush cache
	}
	
	del_vpngateway_route() {
		$IPROUTE route $route_syntax_del "$VPNGATEWAY"
		$IPROUTE route flush cache
	}
	
	set_default_route() {
		$IPROUTE route | grep '^default' | fix_ip_get_output > "$DEFAULT_ROUTE_FILE"
		$IPROUTE route replace default dev "$TUNDEV"
		$IPROUTE route flush cache
	}
	
	set_network_route() {
		NETWORK="$1"
		NETMASK="$2"
		NETMASKLEN="$3"
		$IPROUTE route replace "$NETWORK/$NETMASKLEN" dev "$TUNDEV"
		$IPROUTE route flush cache
	}
	
	reset_default_route() {
		if [ -s "$DEFAULT_ROUTE_FILE" ]; then
			$IPROUTE route replace `cat "$DEFAULT_ROUTE_FILE"`
			$IPROUTE route flush cache
			rm -f -- "$DEFAULT_ROUTE_FILE"
		fi
	}
	
	del_network_route() {
		NETWORK="$1"
		NETMASK="$2"
		NETMASKLEN="$3"
		$IPROUTE route $route_syntax_del "$NETWORK/$NETMASKLEN" dev "$TUNDEV" 
		$IPROUTE route flush cache
	}
else # use route command
	get_default_gw() {
		# isn't -n supposed to give --numeric output?
		# apperently not...
		# Get rid of lines containing IPv6 addresses (':')
		netstat -r -n | awk '/:/ { next; } /^(default|0\.0\.0\.0)/ { print $2; }'
	}
	
	set_vpngateway_route() {
		route add -host "$VPNGATEWAY" $route_syntax_gw "`get_default_gw`"
	}

	del_vpngateway_route() {
		route $route_syntax_del -host "$VPNGATEWAY"
	}
	
	set_default_route() {
		DEFAULTGW="`get_default_gw`"
		echo "$DEFAULTGW" > "$DEFAULT_ROUTE_FILE"
		route $route_syntax_del default
		route add default $route_syntax_gw "$INTERNAL_IP4_ADDRESS"
	}
	
	set_network_route() {
		NETWORK="$1"
		NETMASK="$2"
		NETMASKLEN="$3"
		del_network_route "$NETWORK" "$NETMASK" "$NETMASKLEN"
		route add -net "$NETWORK" $route_syntax_netmask "$NETMASK" $route_syntax_gw "$INTERNAL_IP4_ADDRESS"
	}
	
	reset_default_route() {
		if [ -s "$DEFAULT_ROUTE_FILE" ]; then
			route $route_syntax_del default
			route add default $route_syntax_gw `cat "$DEFAULT_ROUTE_FILE"`
			rm -f -- "$DEFAULT_ROUTE_FILE"
		fi
	}
	
	del_network_route() {
		case "$OS" in
		Linux|NetBSD|Darwin) # and probably others...
			# routes are deleted automatically on device shutdown
			return
			;;
		esac
		NETWORK="$1"
		NETMASK="$2"
		NETMASKLEN="$3"
		route $route_syntax_del -net "$NETWORK" $route_syntax_netmask "$NETMASK" $route_syntax_gw "$INTERNAL_IP4_ADDRESS"
	}
fi

# =========== resolv.conf handling ====================================

# =========== resolv.conf handling for any OS =========================

modify_resolvconf_generic() {
	grep '^#@VPNC_GENERATED@' /etc/resolv.conf > /dev/null 2>&1 || cp -- /etc/resolv.conf "$RESOLV_CONF_BACKUP"
	NEW_RESOLVCONF="#@VPNC_GENERATED@ -- this file is generated by vpnc
# and will be overwritten by vpnc
# as long as the above mark is intact"

	# Remember the original value of CISCO_DEF_DOMAIN we need it later
	CISCO_DEF_DOMAIN_ORIG="$CISCO_DEF_DOMAIN"
	# Don't step on INTERNAL_IP4_DNS value, use a temporary variable
	INTERNAL_IP4_DNS_TEMP="$INTERNAL_IP4_DNS"
	exec 6< "$RESOLV_CONF_BACKUP"
	while read LINE <&6 ; do
		case "$LINE" in
			nameserver*)
				if [ -n "$INTERNAL_IP4_DNS_TEMP" ]; then
					read ONE_NAMESERVER INTERNAL_IP4_DNS_TEMP <<-EOF
	$INTERNAL_IP4_DNS_TEMP
EOF
					LINE="nameserver $ONE_NAMESERVER"
				else
					LINE=""
				fi
				;;
			search*)
				if [ -n "$CISCO_DEF_DOMAIN" ]; then
					LINE="$LINE $CISCO_DEF_DOMAIN"
					CISCO_DEF_DOMAIN=""
				fi
				;;
			domain*)
				if [ -n "$CISCO_DEF_DOMAIN" ]; then
					LINE="domain $CISCO_DEF_DOMAIN"
					CISCO_DEF_DOMAIN=""
				fi
				;;
		esac
		NEW_RESOLVCONF="$NEW_RESOLVCONF
$LINE"
	done
	exec 6<&-
	
	for i in $INTERNAL_IP4_DNS_TEMP ; do
		NEW_RESOLVCONF="$NEW_RESOLVCONF
nameserver $i"
	done
	if [ -n "$CISCO_DEF_DOMAIN" ]; then
		NEW_RESOLVCONF="$NEW_RESOLVCONF
search $CISCO_DEF_DOMAIN"
	fi
	echo "$NEW_RESOLVCONF" > /etc/resolv.conf

	if [ "$OS" = "Darwin" ]; then
		case "`uname -r`" in
			# Skip for pre-10.4 systems
			4.*|5.*|6.*|7.*)
				;;
			# 10.4 and later require use of scutil for DNS to work properly
			*)
				OVERRIDE_PRIMARY=""
				if [ -n "$CISCO_SPLIT_INC" ]; then
					if [ $CISCO_SPLIT_INC -lt 1 ]; then
						# Must override for correct default route
						# Cannot use multiple DNS matching in this case
						OVERRIDE_PRIMARY='d.add OverridePrimary # 1'
					fi
				fi
				# Uncomment the following if/fi pair to use multiple
				# DNS matching when available.  When multiple DNS matching
				# is present, anything reading the /etc/resolv.conf file
				# directly will probably not work as intended.
				#if [ -z "$CISCO_DEF_DOMAIN_ORIG" ]; then
					# Cannot use multiple DNS matching without a domain
					OVERRIDE_PRIMARY='d.add OverridePrimary # 1'
				#fi
				scutil >/dev/null 2>&1 <<-EOF
					open
					d.init
					d.add ServerAddresses * $INTERNAL_IP4_DNS
					set State:/Network/Service/$TUNDEV/DNS
					d.init
					# next line overrides the default gateway and breaks split routing
					# d.add Router $INTERNAL_IP4_ADDRESS
					d.add Addresses * $INTERNAL_IP4_ADDRESS
					d.add SubnetMasks * 255.255.255.255
					d.add InterfaceName $TUNDEV
					$OVERRIDE_PRIMARY
					set State:/Network/Service/$TUNDEV/IPv4
					close
				EOF
				if [ -n "$CISCO_DEF_DOMAIN_ORIG" ]; then
					scutil >/dev/null 2>&1 <<-EOF
						open
						get State:/Network/Service/$TUNDEV/DNS
						d.add DomainName $CISCO_DEF_DOMAIN_ORIG
						d.add SearchDomains * $CISCO_DEF_DOMAIN_ORIG
						d.add SupplementalMatchDomains * $CISCO_DEF_DOMAIN_ORIG
						set State:/Network/Service/$TUNDEV/DNS
						close
					EOF
				fi
				;;
		esac
	fi
}

restore_resolvconf_generic() {
	if [ ! -e "$RESOLV_CONF_BACKUP" ]; then
		return
	fi
	grep '^#@VPNC_GENERATED@' /etc/resolv.conf > /dev/null 2>&1 && cat "$RESOLV_CONF_BACKUP" > /etc/resolv.conf
	rm -f -- "$RESOLV_CONF_BACKUP"

	if [ "$OS" = "Darwin" ]; then
		case "`uname -r`" in
			# Skip for pre-10.4 systems
			4.*|5.*|6.*|7.*)
				;;
			# 10.4 and later require use of scutil for DNS to work properly
			*)
				scutil >/dev/null 2>&1 <<-EOF
					open
					remove State:/Network/Service/$TUNDEV/IPv4
					remove State:/Network/Service/$TUNDEV/DNS
					close
				EOF
				;;
		esac
	fi
}
# === resolv.conf handling via /sbin/modify_resolvconf (Suse) =====================

# Suse provides a script that modifies resolv.conf. Use it because it will
# restart/reload all other services that care about it (e.g. lwresd).

modify_resolvconf_suse()
{
	RESOLV_OPTS=''
	test -n "$INTERNAL_IP4_DNS" && RESOLV_OPTS="-n \"$INTERNAL_IP4_DNS\""
	test -n "$CISCO_DEF_DOMAIN" && RESOLV_OPTS="$RESOLV_OPTS -d $CISCO_DEF_DOMAIN"
	test -n "$RESOLV_OPTS" && eval /sbin/modify_resolvconf modify -s $SCRIPTNAME -p $SCRIPTNAME -f $FULL_SCRIPTNAME -e $TUNDEV $RESOLV_OPTS -t \"This file was created by $SCRIPTNAME\"
}

# Restore resolv.conf to old contents on Suse
restore_resolvconf_suse()
{
	/sbin/modify_resolvconf restore -s vpnc -p $SCRIPTNAME -f $FULL_SCRIPTNAME -e $TUNDEV
}

# === resolv.conf handling via /sbin/resolvconf (Debian, Ubuntu, Gentoo)) =========

modify_resolvconf_manager() {
	NEW_RESOLVCONF=""
	for i in $INTERNAL_IP4_DNS; do
		NEW_RESOLVCONF="$NEW_RESOLVCONF
nameserver $i"
	done
	if [ -n "$CISCO_DEF_DOMAIN" ]; then
		NEW_RESOLVCONF="$NEW_RESOLVCONF
domain $CISCO_DEF_DOMAIN"
	fi
	echo "$NEW_RESOLVCONF" | /sbin/resolvconf -a $TUNDEV
}

restore_resolvconf_manager() {
	/sbin/resolvconf -d $TUNDEV
}

# ========= Toplevel state handling  =======================================

kernel_is_2_6_or_above() {
	case `uname -r` in
		1.*|2.[012345]*)
			return 1
			;;
		*)
			return 0
			;;
	esac
}

do_pre_init() {
	if [ "$OS" = "Linux" ]; then
		if (exec 6<> /dev/net/tun) > /dev/null 2>&1 ; then
			:
		else # can't open /dev/net/tun
			test -e /proc/sys/kernel/modprobe && `cat /proc/sys/kernel/modprobe` tun 2>/dev/null
			# fix for broken devfs in kernel 2.6.x
			if [ "`readlink /dev/net/tun`" = misc/net/tun \
				-a ! -e /dev/net/misc/net/tun -a -e /dev/misc/net/tun ] ; then
				ln -sf /dev/misc/net/tun /dev/net/tun
			fi
			# make sure tun device exists
			if [ ! -e /dev/net/tun ]; then
				mkdir -p /dev/net
				mknod -m 0640 /dev/net/tun c 10 200
			fi
			# workaround for a possible latency caused by udev, sleep max. 10s
			if kernel_is_2_6_or_above ; then
				for x in `seq 100` ; do
					(exec 6<> /dev/net/tun) > /dev/null 2>&1 && break;
					sleep 0.1
				done
			fi
		fi
	elif [ "$OS" = "FreeBSD" ]; then
		if [ ! -e /dev/tun ]; then
			kldload if_tun
		fi
	elif [ "$OS" = "GNU/kFreeBSD" ]; then
		if [ ! -e /dev/tun ]; then
			kldload if_tun
		fi
	elif [ "$OS" = "NetBSD" ]; then
		:
	elif [ "$OS" = "OpenBSD" ]; then
		:
	elif [ "$OS" = "SunOS" ]; then
		:
	elif [ "$OS" = "Darwin" ]; then
		:
	fi
}

do_connect() {
	if [ -n "$CISCO_BANNER" ]; then
		echo "Connect Banner:"
		echo "$CISCO_BANNER" | while read LINE ; do echo "|" "$LINE" ; done
		echo
	fi
	
	do_ifconfig
	set_vpngateway_route
	if [ -n "$CISCO_SPLIT_INC" ]; then
		i=0
		while [ $i -lt $CISCO_SPLIT_INC ] ; do
			eval NETWORK="\${CISCO_SPLIT_INC_${i}_ADDR}"
			eval NETMASK="\${CISCO_SPLIT_INC_${i}_MASK}"
			eval NETMASKLEN="\${CISCO_SPLIT_INC_${i}_MASKLEN}"
			if [ $NETWORK != "0.0.0.0" ]; then
				set_network_route "$NETWORK" "$NETMASK" "$NETMASKLEN"
			else
				set_default_route
			fi
			i=`expr $i + 1`
		done
		for i in $INTERNAL_IP4_DNS ; do
			set_network_route "$i" "255.255.255.255" "32"
		done
	else
		set_default_route
	fi
	
	if [ -n "$INTERNAL_IP4_DNS" ]; then
		$MODIFYRESOLVCONF
	fi
}

do_disconnect() {
	if [ -n "$CISCO_SPLIT_INC" ]; then
		i=0
		while [ $i -lt $CISCO_SPLIT_INC ] ; do
			eval NETWORK="\${CISCO_SPLIT_INC_${i}_ADDR}"
			eval NETMASK="\${CISCO_SPLIT_INC_${i}_MASK}"
			eval NETMASKLEN="\${CISCO_SPLIT_INC_${i}_MASKLEN}"
			if [ $NETWORK != "0.0.0.0" ]; then
				# FIXME: This doesn't restore previously overwritten
				#        routes.
				del_network_route "$NETWORK" "$NETMASK" "$NETMASKLEN"
			else
				reset_default_route
			fi
			i=`expr $i + 1`
		done
		for i in $INTERNAL_IP4_DNS ; do
			del_network_route "$i" "255.255.255.255" "32"
		done
	else
		reset_default_route
	fi
	
	del_vpngateway_route
	
	if [ -n "$INTERNAL_IP4_DNS" ]; then
		$RESTORERESOLVCONF
	fi
	destroy_tun_device
}

#### Main

if [ -z "$reason" ]; then
	echo "this script must be called from vpnc" 1>&2
	exit 1
fi

case "$reason" in
	pre-init)
		do_pre_init
		;;
	connect)
		do_connect
		;;
	disconnect)
		do_disconnect
		;;
	*)
		echo "unknown reason '$reason'. Maybe vpnc-script is out of date" 1>&2
		exit 1
		;;
esac

exit 0
